Method for position control in optical data carriers with address information

ABSTRACT

Track jumping on optical storage media whose address information items invalidate the track error signal (TE) at time intervals is intended to be configured more securely and more reliably. For this purpose, at the end of a coarse jump, one or more correction jumps are carried out if the optical scanner ( 1 ) is not presently sweeping over an address information area and the track change frequency of the tracks crossed by the scanner ( 1 ) falls below a predetermined value.

[0001] The present invention relates to an apparatus and a method forcarrying out position control of an optical scanner on the tracks of adata carrier. In particular, the invention relates to the performance oftrack jumps in optical storage media whose information tracks areinterrupted by addressing information items.

[0002] A drive for reading from and writing to an optical storage mediumis usually equipped with an optical scanner whose scanning beam isdirected onto the optical storage medium by means of an objective lens.This objective lens is finely positioned relative to the tracks of thestorage medium by means of an actuator. The optical scanner togetherwith the actuator is coarsely positioned by a driving motor. A trackjump is typically effected, then, by coarse movement of the scanner bymeans of the driving motor, by counting-down of crossed tracks andacceleration or deceleration of the actuator for fine movement of thescanner with the aid of temporally predetermined pulses. This applies tooptical storage media which do not have address information items in theform of prepits that are laterally offset with respect to the track, andin which the information is stored only in depressions (groove).However, in the presence of optical storage media whose information isstored both in depressions (groove) and elevations (land), a track jumpin this way is no longer possible in a straightforward manner.

[0003] In optical data carriers in which information items are storedonly in groove tracks, such as e.g. CD, CD-ROM, CD-VIDEO, CD-R, CD-RW,DVD-ROM, DVD-R and DVD-RW, the signals TZC and MZC are used in order todetect the position of the scanning beam with respect to the track. Inthis case, e.g. the signals TZC (Track Zero Cross) and MZC (Mirror ZeroCross) can be obtained from the track error and mirror signals. TZC isgenerated by comparing the track error signal TE with zero with the aidof a comparator. The track error signal itself can be derived with theaid of various track error forming methods (e.g. push-pull, DPP, DPD,3-beam, . . . ). The TZC signal exhibits a change in its output signal(edge) whenever the centre of groove or the centre of land is reached.Since useful data are stored only on groove, the MZC signal canadditionally be evaluated in order to find the centre of the informationtrack. The MZC signal is likewise formed with the aid of a comparator.The summation signal of selected detectors is subjected to low-passfiltering in order to filter out the high-frequency signal components ofthe stored information items (pits) and to obtain a signal proportionalto the average reflectivity. This signal is often called the mirrorsignal. In the case of the abovementioned disc formats, the averagereflectivity differs between the written tracks (typically groove,series of pits) and the unwritten areas in between (typically land). Acomparator compares the mirror signal with the comparator level CL,generally zero, and thus generates the signal MZC. An alternative tothis, see FIG. 2, exploits the property that the HF modulation isgreatest on track centres and the lower envelope of the HF signalexhibits a low reflection factor, whereas exactly between the tracks theHF modulation is small and the lower envelope exhibits a higherreflection factor. In order to detect this, the lower envelope (HFE) isformed from the DC-coupled HF signal by peak value detection. The outputsignal of this peak value detector is applied to a comparator eitherdirectly or after passing through a low-pass filter, which comparatorcompares its input signal with a threshold value (comparator level) andgenerates the binarized signal MZC.

[0004] The signal TZC typically has its zero crossing in the centre ofgroove or land, whereas the signal MZC typically has its zero crossingprecisely at the edges between groove and land, or between land andgroove. This relationship results in a phase shift of ±90° between thesignals TZC and MZC. This phase shift enables unambiguous detection ofthe direction of movement of the scanning beam of the optical unit withregard to the current track position, which can be derived from thestate “Cond” depicted in FIG. 2, which may lie between 0 and 3.

[0005] In most of the abovementioned optical storage media, no addressinformation items are provided in a form which occasionally invalidatesor interrupts the track error signal. Since the storage of the usefulinformation items is envisaged only in depressions, so-called grooves,the MZC signal always has a specific value when the track centre of thegrooves is reached. Thus, in these storage media, in order to switch onthe track regulator, it is necessary only to wait for the TZC signal tohave an edge when the MZC signal simultaneously shows the centre of theinformation track. As a further criterion, however, as described above,the relative speed between the scanning beam and the tracks on the discshould be detected, so that the track regulator is able to reduce theremaining kinetic energy. Shortly before the regulator is switched on,the fact of whether the relative speed is low enough actually to enablethe regulator to be switched on successfully is usually detected byevaluation of the frequency of the track crossings.

[0006] In DVD-RAM discs, it is not possible to generate the signal MZCin the manner described above. When recording media of this type areused, it is not possible, in the course of the crossing of the tracks inthe radial direction, to obtain information about the direction in whichthe light beam crosses the tracks of the recording medium. The so-calledmirror signal MZC which is generated for this purpose in conventionaldata carriers and detects a region free of data markings, the so-calledmirror area, has double the frequency in land-and-groove recordingmedia. Track and intermediate track, owing to the data markings presentthere, have a lower reflectivity than the region which is locatedbetween track and intermediate track and in which the mirror signal thenhas its maximum. Consequently, a comparison of the phase angle of thetrack error signal and of the mirror signal for direction identificationis no longer meaningful on account of the doubled frequency of themirror signal.

[0007] An object of the present invention consists in proposing a methodand an apparatus which reliably and rapidly ensure the track coupling-inof the scanning beam after a track jump, even in optical storage mediawhose tracks are interrupted by header areas. Preferably, this reliableand rapid track coupling-in is also intended to be ensured for DVD-RAMdiscs, in which both the groove tracks and the land tracks containinformation items. According to the present invention, this object isachieved by means of a method according to claim 1 and an apparatusaccording to claim 7. Preferred developments are defined in thesubordinate claims.

[0008] The accompanying drawings serve for elucidating the invention ingreater detail. In the drawings:

[0009]FIG. 1 shows a block diagram of an apparatus according to theinvention;

[0010]FIG. 2 shows the unambiguity of the phase angle of TZC and MZCsignal with regard to the error signal TE

[0011]FIG. 3 shows a signal profile diagram in the event of a trackjump;

[0012]FIG. 4 shows a signal profile diagram in the event of anothertrack jump;

[0013]FIG. 5 shows a signal profile diagram of a further track jump; and

[0014]FIG. 6 shows a signal profile diagram of yet another track jump.

[0015] The present invention will now be illustrated using a preferredexemplary embodiment.

[0016] A track jump is generally effected in a number of steps. Firstly,as has already been explained, a coarse jump is carried out in thedirection of the destination track by the entire optical scanner beingmoved by a driving motor. After the coarse jump, generally a trackregulating circuit is closed in order that the scanner is temporarilystabilized on a track. Afterwards, if necessary, one or more correctionjumps are carried out by the scanning beam being moved by an actuatorwhich performs the fine positioning of the scanner.

[0017] Before the track regulating circuit is closed in DVD-RAM storagemedia or similar media, it is necessary to check various states andconditions of the optical scanning system and, in particular, of thescanning beam. In particular, the regulator must be prevented from beingclosed at instants at which the track error signal is not valid. This isthe case primarily when the scanning beam is currently sweeping over theaddress information items (prepits of the header) not arranged in thetrack centre. Furthermore, before the track regulator is switched on, itmust be ensured that the chosen track polarity corresponds to that ofthe jump destination since the destination information may lie both ongroove and on land and the chosen track polarity must correspond to thetype of destination track. A further difficulty results from therelatively rapid sequence of stored address information items.

[0018] A coupling-in or track jump operation should be ended within thetime interval between two address information items. It is advantageousfor the track regulator to be closed only in proximity to the trackcentre, that is to say when the track error signal TE is almost zero.Furthermore, at the coupling-in instant near the track centre, therelative speed between the scanning beam and the tracks on the discshould also be reduced to an extent such that the track regulator isable to reduce the remaining kinetic energy. In principle, witheccentric discs, this is the case only when the relative movement in thetrack transverse direction between tracks on the disc and the actuatorcurrently exhibits a change in direction. Owing to the ever smallertrack spacings and the ever higher rotational speeds of present andfuture high-density storage media, this problem will be furtherintensified since the address information items succeed one another moreand more rapidly at higher rotational speeds but the stabilization timefor switching on the track regulator cannot be shortened arbitrarily.One aspect of the invention resides in activating the regulator notexactly on the destination track but also already in proximity theretoand then reaching the destination by means of correction jumps. In thiscase, it should be noted that the actual destination track and the trackon which the track regulator is to be momentarily activated may bepossibly be of different types and, accordingly, have different trackpolarities.

[0019] These boundary conditions also exist analogously in the case ofmedia whose useful information is admittedly stored only on groove, butwhose address information items likewise occasionally invalidate thetrack error information TE. In contrast to DVD-RAM, however, in thiscase the polarity of the track error signal TE is always the same since,after all, information is never read from land tracks or writtenthereto.

[0020] If a track jump over a relatively long jump distance is theninitiated, then the track regulating circuit is opened and the scanneris displaced by the jump distance by motor, so-called coarse jump withtrack motor. This is done by counting down the tracks to be crossed.Having arrived at the jump destination, which, if appropriate, is only aprovisional destination, the coarse jump is ended and an attempt is madeto close the track regulating circuit at the destination position. Sincethe destination position may lie on a groove or on a land, all theabove-described conditions or criteria for closing the regulatingcircuit should be fulfilled simultaneously. They are:

[0021] a) track error signal TE is valid, i.e. address information itemsare not read, no header area is swept over

[0022] b) scanning beam is in proximity to a track centre, TE is almostzero

[0023] c) relative speed is low, that is to say, for example, that theTZC frequency is sufficiently low

[0024] d) preset track polarity (groove/land) is identical to that ofthe jump destination,

[0025] e) time interval until traversal of the next address informationitem is longer than the time required for regulator stabilization.

[0026] In optical storage media which only contain information items ongroove tracks, criterion d) is to be replaced by the criterion d′) thecurrent track is identical to the destination track.

[0027] To a certain extent, criteria c) and d) have opposing properties.This stems from the fact that, at a sufficiently low TZC frequency, thefrequency of a corresponding polarity signal is also low. Accordingly,there is, in principle, a 50% probability that criteria a) to c) arefulfilled but the predetermined regulating parameter of track polarityfor position regulation of the scanning beam does not currentlycorrespond to the track polarity of the destination track, that is tosay groove or land, on which the regulating circuit is to be closed.Since only the time interval between the address information items is ineach case available for closing the track regulator, the theoreticalpossibility exists that, between the successive address informationitems, the destination track with the polarity sought, criterion d),never coincides temporally with the other criteria since the change inpolarity takes place too slowly. Moreover, owing to the currently lowrelative speed, it is unlikely that the scanning beam will reach thedestination track within the time interval between two addressinformation items.

[0028] Equally, in the case of optical storage media which only containinformation items on groove tracks, to a certain extent criteria c) andd) may have opposing properties. This stems from the fact that, at asufficiently low TZC frequency, there is a 50% probability that criteriaa) to c) are fulfilled but the scanning beam does not currently lie onthe destination track. Since only the time interval between the addressinformation items is in each case available for closing the trackregulator, the theoretical possibility exists that, between successiveaddress information items, the destination track (criterion 4 a) nevercoincides temporally with the other criteria. Moreover, owing to thecurrently low relative speed, it is unlikely that the scanning beam willreach the destination track within the time interval between two addressinformation items.

[0029] In order to solve the problem, two solutions are proposedaccording to the invention:

[0030] If criteria a) to c) are fulfilled simultaneously, but criteriond) destination track polarity or d′) destination track is not fulfilled,then firstly the regulating circuit is closed on one of the secondarytracks. To that end, before the track regulator is switched on on one ofthe secondary tracks, the respectively matching track polarity isdetermined from a groove/land signal (G/L signal) obtained from thescanner and is set correctly. This is not necessary in the case of mediawhose information items are stored only on groove. After traversal ofthe next address information item (header), one or more correction jumpsare then carried out, if necessary, with simultaneous changeover of thetrack polarity. If the position of the next address information item isstill far enough away, it is advantageous for the correction jump stillto be carried out before the next address information item. To that end,it is important to know the stabilization time of the track regulatorand the time before the next address information item is reached. Shouldthe anticipated stabilization time be longer than the time remainingbefore the next address information item, then the correction jump isdelayed until the next address information item has been passed.

[0031] In accordance with the second solution, the track regulator isnot closed and the scanner is not stabilized on a secondary track beforethe correction jump is initiated, which stabilizes the scanning beam atany rate on the desired track type. In this case, too, what is crucialfor the initiation of the correction jump is whether the correction jumpcan be reliably ended before the next address information item is read.

[0032] In both cases, the correction jump can be effected in atemporally controlled manner or with the aid of evaluation of the TEsignal. In the case of time control, predetermined pulse lengths ofacceleration or braking pulses are used, which displace the actuator bythe distance from groove to land, or vice versa.

[0033] In one exemplary embodiment, during such a correction jump, theinstantaneous position of the actuator relative to the track is acquiredby evaluation of zero crossing and maximum value of the TE signal. As analternative, instead of acquiring the maximum value of the TE signal, itis also possible to use the G/L signal.

[0034] If the scanning beam is displaced from groove to land, or viceversa, then the TE signal will assume a maximum value once during thisjump. This maximum value of this TE amplitude occurs when the scanningbeam is situated exactly between groove and land. In other words, thismaximum amplitude identifies exactly half the distance between groovecentre and land centre. Thus, if the intention is to effect for examplea correction jump from groove to land, then, in accordance with thefirst solution, the track regulating circuit is opened and the actuatoris accelerated by an acceleration pulse until the TE signal has assumeda maximum value. From here, the actuator is decelerated by a brakingpulse of the same length. The track regulator can then be switched onagain. As an alternative, it is possible, as already mentioned, to usethe switching edge of the signal G/L for ending the acceleration pulseor starting the braking pulse, since the switching edge occurs at thesame position of the scanning beam with respect to the track as themaximum of the track error signal TE.

[0035] In accordance with the second solution, even without momentarilyclosing the track regulating circuit, the zero crossing of the TE signalfrom the secondary track is awaited and then the procedure is asdescribed above. In both cases, however, it must be ensured that thetime for execution of the correction jump is not longer than the timeremaining until the next address information item is swept over.

[0036] As an alternative, the deceleration pulse of the actuator canalso last until the zero crossing of the TE signal on the destinationtrack has been reached. Afterwards, the track regulator can be activatedagain.

[0037]FIG. 1 shows an exemplary embodiment according to the inventionfor realization of the jump function described. FIGS. 3 to 6 useexamples to show track search operations with the most important signalprofiles.

[0038] An optical scanner 1 contains an actuator 2, which is suspendedsuch that it can move in the vertical and horizontal direction, and alsothe objective lens 19 mounted therein. The scanner 1 supplies theindividual detector signals of its photodetector to a signal matrix 3,which forms the signals data signal HF, track error signal TE andgroove/land signal G/L′ from the individual signals by addition andsubtraction. An address decoder 4 extracts the addresses ADR from thedata stream HF read by the scanner 1 and supplies them to a CPU 5. A G/Ldetector 6 extracts the signal G/L from the signal G/L′ supplied fromthe scanner 1, which signal G/L is used for track counting, fordetermining the position of the scanning beam relative to the track, andalso for controlling the jump process. A maximum value detector 7outputs a signal when a maximum value of the track error signal TE hasbeen found. It comprises e.g. a differentiator and a comparator and canlikewise be used for determining the position of the scanning beamrelative to the track. A track zero crossing detector 8 changes itsoutput level whenever the track error signal TE changes the sign. Thesignal TZC from the track zero crossing detector 8 and the signal TEMAXfrom the maximum value detector 7 or the signal G/L from the G/Ldetector 6 feed the jump time controller 91 which can be enabled by theCPU 5 and then triggers a correction jump as described above.

[0039] If the track regulation loop is to be closed, then this is doneby activation of a regulator 10. In accordance with the track on whichthe track regulator is to be activated (groove or land), the CPU 5interrogates the signal G/L and, accordingly, correctly sets the trackpolarity at the polarity switch 11 prior to the activation of theregulator 10.

[0040] The following functions are typically processed in the CPU 5 bymeans of a program, but, with a certain outlay, they can also berealized in hardware as a sequence control, for example in the form of aso-called state machine or the like.

[0041] An address sequence time controller 12 enables track jumps onlywithin specific time intervals. The signal TE must be valid for thispurpose and, before the sweeping-over of the next address informationitem from the address decoder 4, enough time must remain in order thatthe regulator transient recovery time is not undershot and/or in orderthat a correction jump can be reliably executed. The address sequencetime controller 12 emits a signal JA with “high” level if a track jumpis enabled, otherwise the signal CA has the “low” level. A track jumpcalculator 13 uses the instantaneous position of the scanning beam,which it obtains from the address decoder 4 and the destination positionto calculate the number of tracks to be crossed. A comparator 14compares the number of tracks counted by a track counter 15 with thevalue calculated in the track jump calculator 13 and outputs a successsignal to a track jump supervisor 16 if the number of tracks crossed hasreached the calculated value. As input signals, the track counter 15receives the TZC signal from the track zero crossing detector 8 and theG/L signal from the G/L detector 6. The track jump supervisor 16interrogates whether the track crossing speed VTC measured by a trackcrossing speed measuring unit 17 by means of the TZC signal issufficiently low, whether, in accordance with the G/L signal, thedestination track (groove or land) has been reached, whether the tracksignal error values TE determined by the window comparator 18 do notexceed a predetermined value (track centre should be near) and whether,in accordance with the signal JA from the address sequence timecontroller 12, enough time remains in order to close and stabilize theregulator prior to the reading of the next address information item. Thetrack jump supervisor 16 supplies a tracking enable signal ENT to theregulator 10 and, in accordance with the determined track type (G/L) ofthe provisional jump destination, a track polarity signal TPOL to thepolarity switch 11. It furthermore supplies a jump enabling signal ENJand the corresponding jump direction JD to the jump time controller 9.

[0042] The end of a track jump will be explained below using threeexamples. In the examples, the provisional jump destination shall bereached, the coarse advance of the scanner has already been switchedoff, and the track crossing speed of the actuator shall already bereduced.

[0043] Some of the tracks of an optical data carrier are indicateddiagrammatically in the top right region of each of FIGS. 3-6. Thetracks run from left to right; they are each identified by their tracktype groove G or land L. The tracks are each interrupted by a headerarea H; three header areas H are shown in each of FIGS. 3-6. Thedestination track is identified by hatching; the direction of movementof the data carrier is indicated by means of an arrow DR. The light spotLS of the scanning beam is depicted symbolically at a few locations onits path—identified by LST—over the tracks. It moves from left to rightin each case in the figure. To the left of the tracks, the track errorsignal TE is specified as a function of the location x perpendicular tothe tracks. Below the tracks, a plurality of signal profiles arespecified as a function of the time or the location y in the trackdirection. From top to bottom, they are the tracking enable signal ENT,the track error signal TE, the actuator signal TAKT emitted by theregulator 10 to the scanner 1, the track polarity signal TPOL, thegroove/land signal G/L, the track crossing signal TZC and also a signalJA which specifies whether a jump can be begun at a specific instant orcorresponding location, and can be ended before reaching the next headerarea, or whether this is not the case.

[0044]FIG. 3 shows an example in which the destination sector lies on aland track. Since the preconditions

[0045] a) track error signal TE is valid, address information item(header) is not currently being swept over

[0046] b) track centre is near (TE almost zero); and

[0047] c) relative speed is low (TZC frequency is sufficiently low)

[0048] are already satisfied shortly before reaching the destinationtrack, the regulator 10 is already activated on the groove track beforethe final destination track. The CPU 5 interrogates the information G/Land activates the track regulator 10 with the correct track polarity.Since the condition

[0049] e) time interval until traversal of the next address informationitem is longer than regulator stabilization time

[0050] is no longer satisfied, the sweeping over of an addressinformation item is still awaited before the subsequent correction jump.Afterwards, condition

[0051] d) track polarity (groove/land) is identical to the jumpdestination

[0052] is also satisfied by means of a correction jump. To that end,acceleration and braking pulses are applied to the actuator. At the sametime, the track polarity is set in accordance with the destinationtrack. The length Δt1 of the acceleration pulse of the actuator 2 isprescribed by the signal G/L or the TE maximum value detector 7; thelength Δt3 of the braking pulse is oriented to the edge of TZC. Thetrack jump is thus ended.

[0053] There is a 50% chance of all five conditions being satisfiedsimultaneously. In this case, the jump destination is reached directly,without a correction jump.

[0054]FIG. 4 likewise shows an example in which the destination sectorlies on a land track. Since the preconditions

[0055] a) track error signal TE is valid, address information item(header) is not currently being swept over

[0056] b) track centre is near (TE almost zero); and

[0057] c) relative speed is low (TZC frequency is sufficiently low)

[0058] are already satisfied shortly before reaching the destinationtrack in this case, too, the regulator 10 is already activated on thegroove track before the destination track. The CPU 5 interrogates theinformation G/L and activates the track regulator 10 with the correcttrack polarity. The track regulating circuit is closed for the purposeof stabilization; since the condition

[0059] e) time interval until traversal of the next address informationitem is longer than regulator stabilization time

[0060] is also satisfied, the sweeping over of an address informationitem is not still awaited before the correction jump, rather condition

[0061] d) track polarity (groove/land) is identical to the jumpdestination

[0062] is also satisfied by means of a correction jump still before thenext address information item. To that end, acceleration and brakingpulses are applied to the actuator. At the same time, the track polarityTPOL is set in accordance with the destination track. The length Δt1 ofthe acceleration pulse of the actuator 2 is prescribed by the signal G/Lor the TE maximum value detector 7; the length Δt2 of the braking pulseis in this case chosen to be the same as the length Δt1. The track jumpis thus ended.

[0063]FIG. 5 likewise shows an example in which the destination sectorlies on a land track. Since the preconditions

[0064] a) track error signal TE is valid, address information item(header) is not currently being swept over

[0065] b) track centre is near (TE almost zero); and

[0066] c) relative speed is low (TZC frequency is sufficiently low)

[0067] are satisfied only shortly after reaching the destination track,the track position is ascertained from the zero crossing of the trackerror signal TE. The CPU 5 interrogates the information G/L and checkswhether the current track type corresponds to the destination tracktype. Since this is not the case here, but the condition

[0068] e) time interval until traversal of the next address informationitem is longer than regulator stabilization time

[0069] is satisfied, i.e. the signal JA is set to “high”, the sweepingover of an address information item is not still awaited before thecorrection jump. In this case, the correction jump is initiated withoutthe track regulator 10 being closed beforehand. As a result, condition

[0070] d) track polarity (groove/land) is identical to the jumpdestination

[0071] can also be satisfied before reaching the next addressinformation item. To that end, acceleration and braking pulses areapplied to the actuator. At the same time, the track polarity is set inaccordance with the destination track. The length Δt1 of theacceleration pulse of the actuator 2 is prescribed by the signal G/L orthe TE maximum value detector 7; the length Δt3 of the braking pulse isoriented to the edge of TZC.

[0072] Since, in the case of FIG. 5, the kinetic energy of the actuator2 was not reduced by momentary closing of the track regulator 10 beforethe initiation of the correction jump, generally a different pulselength of acceleration pulse and braking pulse is necessary in order tomove the actuator 2 to the destination track. It may be advantageous,therefore, to employ the method outlined in FIG. 4 in order to reducethe residual relative speed of the scanning beam relative to the trackfirstly by activation of the track regulator and then to initiate thecorrection jump.

[0073] The descriptions above can also be applied analogously to mediawhose useful information is admittedly stored only on groove but whoseaddress information likewise occasionally invalidates the track errorinformation. The instantaneous position of the actuator 2 relative tothe track can be detected by evaluating the zero crossings of the TEsignal. It is advantageous additionally to use the MZC signal in orderto monitor the position of the scanning beam and to avoid the ambiguityof the TZC edges. If the scanning beam is displaced from one writtentrack to the next written track, or vice versa, then the TE signal willhave a zero crossing once during this jump. This zero crossing of the TEamplitude occurs when the scanning beam is situated exactly between twowritten tracks. The zero crossing thus identifies exactly half thedistance between track centre and next track centre. At the same time,the signal MZC will show that the scanning beam is not situated on thecentre of a readable track. In other words, if a correction jump by onetrack is to be effected, then, in the first case, the track regulatingcircuit is opened and the actuator 2 is accelerated by an accelerationpulse until the TE signal passes through a zero crossing. From here, theactuator 2 is decelerated by a braking pulse for as long as theacceleration pulse lasted. The track regulator 10 can then be switchedon again. For the second case, even without momentarily closing thetrack regulating circuit, the first zero crossing of the TE signal ofthe secondary track can be awaited and then the procedure is asdescribed above. In both cases, however, it should be ensured that thetime for executing the correction jump is not longer than the timeremaining before the next address information item is swept over. As analternative, the deceleration pulse of the actuator 2 can also lastuntil the zero crossing of the TE signal on the destination track isreached. The track regulator 10 can then be activated again.

[0074] It is likewise advantageously possible to begin a track jump evenbefore a header area, if it is ensured that it is reliably ended onlyafter the sweeping over of this header area in the next or one of thefollowing useful data areas, and no information items disrupted by theheader area are required for jump control. This is the case inparticular with a very high relative speed between data carrier andscanning beam, that is to say, for example, with a high rotational speedof an optical disc, or with very short header areas and/or very shortdistances between two header areas. In this case, the signal JA is to beset to “high” as long as a jump can be begun in the useful data area andbe reliably ended in a following useful data area. The conditions inthis respect are to be chosen or adapted accordingly.

[0075]FIG. 6 shows an example, of a data carrier, in which data arepresent only in groove tracks, and in which the destination track is notimmediately reached. Only the groove tracks G are identified here sincethe L tracks contain no information. Since the preconditions

[0076] a) track error signal TE is valid, address information item(header) is not currently being swept over

[0077] b) track centre is near (TE almost zero); and

[0078] c) relative speed is low

[0079] are already satisfied shortly before reaching the destinationtrack, the regulator 10 is already activated on the track before thedestination track. Since the condition

[0080] e) time interval until traversal of the next address informationitem is longer than regulator stabilization time

[0081] is no longer satisfied, the sweeping over of an addressinformation item is still awaited before the correction jump.Afterwards, condition

[0082] d′) current track is identical to the jump destination is alsosatisfied before by means of a correction jump. To that end,acceleration and braking pulses are applied to the actuator 2. Thelength Δt1 of the acceleration pulse of the actuator 2 is derived fromthe signal TZC; the length Δt2 of the braking pulse is identical to thelength Δt1 of the acceleration pulse. The track jump is thus ended.

[0083] However, in this case, too, there is a 50% probability of allfive conditions being satisfied simultaneously. The jump destination canthen be reached directly, without a correction jump.

[0084] Track jumping on optical storage media whose address informationinvalidates the track error signal TE, or other signals required fortrack jumping, at time intervals is made more secure and more reliableby the methods outlined.

1. Method for position control of an optical scanning device (1, 2) forscanning and/or writing to tracks of a data carrier, having the steps ofproviding a permissibility signal if the optical scanning device (1, 2)sweeps over a useful data area and no address data area, providing atrack proximity signal if the distance between the optical axis of thescanning device (1, 2) and the track centre of a track currently beingswept over is less than a predetermined value, and closing a regulatingcircuit for stabilizing the optical scanning device (1, 2) on a track ifthe permissibility signal and the track proximity signal are provided.2. Method according to claim 1, wherein the regulating circuit is closedonly if a track crossing speed of the optical scanning device (1, 2)falls below a predetermined value.
 3. Method according to claim 1 or 2,wherein the regulating circuit is closed irrespective of whether thetrack type, namely groove or land, of the track currently being sweptover is identical to that of a predetermined destination track. 4.Method according to one of claims 1 to 3, wherein the regulating circuitis closed only if a time interval until traversal of the next addressinformation item to be scanned is sufficient for stabilization of theregulating circuit.
 5. Method for carrying out a track jump, whereinposition control of the optical scanning device (1, 2) according to oneof claims 1 to 4 is effected before and/or after the track jump. 6.Method according to claim 5, wherein the track jump is temporallycontrolled using a position signal obtained from the optical scanningdevice (1, 2).
 7. Apparatus for position control of an optical scanningdevice (1, 2) for scanning and/or writing to tracks of a data carrierhaving an address sequence time control device (12) for outputting apermissibility signal which specifies whether the optical scanningdevice (1, 2) sweeps over a useful data area or address data area, atrack proximity determining device for outputting a track proximitysignal which specifies that the distance between the optical axis of thescanning device (1, 2) and the track centre of a track currently beingswept over is less than a predetermined value, and a track jumpsupervisory device (16) for closing a regulating circuit for stabilizingthe optical scanning device (1, 2) on a track if the permissibilitysignal does not indicate an address data area and the track proximitysignal signals the proximity of the optical axis to a track. 8.Apparatus according to claim 7, wherein provision is furthermore made ofa track crossing speed measuring device (17) for outputting a speedassessment signal which specifies whether a track crossing speed of theoptical scanning device (1, 2) exceeds a predetermined value. 9.Apparatus according to claim 7 or 8, wherein the track proximitydetermining device has a window comparator (18), which can be used toascertain whether a distance between the optical axis of the scanningdevice (1, 2) and the track centre of the track currently being sweptover is less than a predetermined value.
 10. Apparatus according toclaim 7, 8 or 9, wherein the regulating circuit is closed irrespectiveof whether the track type, namely groove or land, of the track currentlybeing swept over is identical to that of a predetermined destinationtrack, and, if appropriate, a correction jump to the destination trackis effected if the track type encountered does not correspond to thetype of the predetermined destination track.
 11. Apparatus according toone of claims 7 to 10, wherein the regulating circuit can be closedexclusively when the address sequence time control device (12)ascertains that a time interval until traversal of the next addressinformation item to be scanned is sufficient for stabilization of theregulating circuit.
 12. Apparatus for carrying out a track jump havingan optical scanning device (1, 2) and an apparatus for position controlaccording to one of claims 7 to 11, wherein position control of theoptical scanning device (1, 2) can be carried out before and/or afterthe track jump.
 13. Apparatus according to claim 12, wherein the trackjump is temporally controlled using a position signal obtained from theoptical scanning device (1, 2).